Measurement and control of polymerization reactions



Sept. 27, 1966 E. D. ToLlN ETAL MEASUREMENT AND CONTROL OFPOLYMERIZATION REACTIONS Original Filed Dec.

9 Sheets-Sheet 1 S -l m n l I l I I I l I I l l l I I I l I I I I l I ll I I l IIJ O NG N m u? l I I I l t I l I l l I l l I Il OL m mn@ I.. HD. A A E W n FLD. Pzoou a Y B ,/v l- .mku 01:00 i mm om mmjomwzoo @z.oul/ ,Q..mm mm m lmwf mzmd vm mmf-- 1 .2... il.. Eroi. fm um I|I|L lEbaoo 25000 .v Elwwf/U m IIQDI.. w m@ :IJ r I IIJ omf\..moko mm m v z LH .rzmom Iw t/ oou 2 sx r- I. .5:00am S I I I I I l l l l l l I l l l Il I I I n l l I I I l l l I I l l Il L rl I I I I I l l l l l l I I l ll l l l l l l l l l l I l l .IIL r l I l l l l l l I I l l l l l l l l ll l l l l l I I l I I'L l l l l l I l I l I l l l l I l I l i l I l l lI l l l I I I l l l I l I I lll- F Sept. 27, 1966 Epo. ToLlN ETAL Y3,275,809

MEASUREMENT AND CONTROL 0F POLYMERIZATION REACTIONS Original File'Dec.4, 1957 9 Sheets-Sheet 3 Cr u .0 D a y 1 .E 9 1 9 `LL g3 INVENToRs E. D.ToLlN D. A. FLUEGEL L A TMR/vers Sept 27, 1966 E. D. roLlN ETAL3,275,809

MEASUREMENT AND CONTROL OF POLYMERIZATION REACTIONS Original Filed Dec.4, 1957 9 Sheets-Sheet 4 40|-i lf\40 G01N SERVO AMPLIFIER INVENTOR E. D.TOLIN D. A. FLUEGEL ,u BY ry 'L Sept. 27, 1966 E. D. Tc| |N ETAL3,275,809

MEASUREMENT AND CONTROL 0F POLYMERIZATION REACTIQNS Original Filed Deca4, 1957 9 Sheets-Sheet 5 A TTORNEYS Sept. 27, 1966 E. D. ToLlN ETALMEASUREMENT AND CONTROL OF POLYMEHIZATION REACTIONS Original Filed Dec.4. 1957 9 Sheets-Sheet 6 b"Il" INVENTORS s. D. ToLl N D. A. F I UEGELSept. 27, 1966 E. D. ToLlN L-:TAL`

MEASUREMENT AND CONTROL OF POLYMERIZATAION REACTIONS Original Filed Dec.4, 1957 9 Sheets-Sheet '7 n NN mmv

mmm

L. rnmm @No ...v I l En www l En \.mmun.w w mmm v fm2 uomv Sept. 27,1966 E. D. roLlN ETAL MEASUREMENT AND CONTROL OF POLYMERIZATIONREACTIONS Original Filed Dec. 4, 1957 9 Sheets-Sheet 8 mmm www

INVENTORS E. D. TOL! N D. A. FLUEGEL Sevf- 21, 196e` E. D. TOLlN ETALMEASUREMENT AND v(JONTROL 0F POLYMERIZATION Original Filed Dec. 4, 1957AMPLIFIER CONVERTER REACTIONS 9 sheets-Sheet 9 AMPLIF'IER f'- AMPLIFIERPULSE 592 GENERATOR TUNED AMPLlFlER INVENTORS ll- E.D. ToLlN D. A.FLUEGEL United States Patent O 3,275,809 MEASUREMENT AND CONTROL OFPOLYMERI- ZATION REACTIONS Ernest D. Tolin and Dale A. Fluegel,Bartlesville, Okla.,

assignors to Phillips Petroleum Company, a corporation of DelawareOriginal application Dec. 4, 1957, Ser. No. 700,612, now Patent No.3,105,896, dated Oct. 1, 1963. Divided and this application Mar. 4,1963, Ser. No. 262,783 Claims. (Cl. 23S-151.12)

This invent-ion relates to apparatus for measuring and controlling therates of polymerization reactions. In another aspect it relates to novelcomputing apparatus.

This application is a division of copending application, Serial No.700,612, filed December 4, 1957, and now Patent No. 3,105,896.

Various methods are known for producing normally solid and semisolidpolymers. For example, hydrocarbons, such as ethylene, propylene,isobutene, butadiene and styrene can be polymerized, eitherindependently or in Various admixtures with one another, to producesolid or semisolid polymers. Recently, considerable attention has beendirected toward the production of solid olen polymers, such as polymersof ethylene and/ or propylene. The polymerizations are frequentlycarried out in the presence of a solid catalyst, utilizing a liquidsolvent as the reaction medium. The polymerization reactions areexothermic so that it becomes necessary to provide for the removal ofheat liberated by the reaction. The removal of the heat of reaction isoften accomplished by employing a reactor provided with :an indirectheat exchange means through which a suitable coolant is circulated. Oneof the problems which occurs when using such a system r involvescontrolling the polymerization reaction rate so 30 that a uniformproduct having desired properties is obtained.

In accordance with the present invention, apparatus is provided for usein measuring the rates of polymerization processes and controlling suchprocesses in an automatic manner. The control -is based upon ameasurement of the heat liberated by the polymerization reaction, whichmeasurement can be made by subtracting the heat supplied to the reactorfrom the heat removed from the reactor. Measurements are made of the owrates and temperatures of all the principal streams entering and leavingthe reactor. Other sources of heat addition and heat losses are alsomeasured to provide an indication of the total amount of heat enteringand leaving the reactor. Cornputing apparatus is provided for solvingsequentially the several heat balance equations which represent theamounts of heat entering or leaving the reactor from the several processstreams. This requires the solution of a plurality of multiplications.The reactor can be controlled in an automatic manner in response to theoutput signal from the computing mechanism. An important feature of thisinvention resides in providing a correction for temperature changeswithin the reactor. Such ternperature changes are measured, and a signalrepresentative thereof modifies the basic control signal.

Accordingly, it is an object of this linvention to provide improvedapparatus for use in measuring and controlling polymerization reactions.

Another object is to provide a means for compensating a heat balancecontrol system for temperature lluctuations 65 in the reactor.

Other objects, advantages and features of the invention should becomeapparent from the following detailed description which is taken inconjunction with the accompanying drawing in which:

FIGURE 1 is a schematic circuit drawing of :a polym- ICC erizationreactor which can be controlled by the apparatus of this invention.

FIGURE 2 is a schematic circuit drawing showing the detecting elementsof FIGURE 1.

FIGURE 3 is a schematic circuit drawing of a portion of the computerwhich establishes signals representative of ilows of the inlet streamsinto the reactor.

FIGURE 4 i-s a schematic circuit drawing of the input terminals of thecomputer and a portion of the automatic balancing mechanism.

FIGURE 5 is a schematic circuit drawing showing a second portion of theautomatic balancing mechanism.

FIGURE 6 is a schematic circuit drawing of a portion of the computer`timing mechanism.

FIGURE 7 is a schematic circuit drawing of one of the multiplicationchannels of the computer.

FIGURE 8 is a schematic circuit drawing of the summing and calibrationnetwork employed in the computer.

FIGURE 9 is a schematic circuit drawing of a second portion of thetiming mechanism.

FIGURE 10 is a schematic circuit drawing of the reactor temperaturecompensating network of this invention.

The present invention -is broadly applicable to polymerization processesin general, and more particularly to processes in which an olen iscontacted with a catalyst in suspension in a solvent. The invention isespecially applicable for use Vin controlling the production of polymersas described in U.S. Patent No. 2,825,721. As set forth in this patentin greater detail, unique polymers and copolymers can be produced bycontacting one or more oleins with la catalyst comprising, as anessential ingredient, chromium oxide, preferably .including asubstantial amount of hexavalent chromium. The chromium oxide isordinarily associated with at least one other oxide, particularly atleast one oxide selected from the group consisting of silica, alumina,zirconia and thoria. The amount of chromium, as chromium oxide, in thecatalyst can range from 0.1 to 10 or more weight percent. Allthoughchromium contents as high as 50 weight percent are operative, amountsabove 10 Weight percent appear to have little added advantage for thepolymerization of ethylene. However, for the polymerization of propyleneand higher boiling oleiins, chromium contents as high as 25 or 30percent are often advantageous. One satisfactory method for producingthe catalyst involves the use of a steam-aged commercial crackingcatalyst comprising a coprecipitated gel containing approximately weightpercent silica and 10 weight percent alumina. Such a gel is impregnatedwith an aqueous solution of a chromium compound ignitable to chromiumoxide. Examples of such compounds are chromium trioxide, chromiumnitrate, chromium acetate and ammonium chromate. The composite resultingfrom the impregnation step is dried and then contacted for a period ofseveral hours at a temperature of from about 450 to 1500 F., preferablyfrom about 900 to 1000 F., for example, with a stream of a substantiallyanhydrous oxygen-containing gas, such as a1r.

The olen feed for the polymerization comprises at least one olefinselected from the class of l-olefins having a maximum of 8 carbon atomsper molecule and no branching nearer the double bond than the4-position. Examples of such oletins include ethylene, propylene, 1-butene, l-pentene and 1,3-butadiene. as ethylene-propylene copolymersand ethylene-butadiene copolymers, can be prepared by the describedmethod. The polymerization can be eected at a temperature in the rangeto 450 F. The pressure can range from approximately atmospheric to ashigh as 1000 p.s.i.

A satisfactory method of conducting the polymerization as disclosed inthe above mentioned patent comprises contacting an olefin with a slurryof catalyst in a hydro- Copolymers, suchv D carbon solvent which canexist as a liquid at the temperature of polymerization. In such aprocedure,.the reaction pressure need only be suiiicient to maintain thesolvent substantially in the liquid phase, and ordinarily ranges fromabout 100 lto 700 p.s.i. The control system ofthe present invention isparticularly applicable to this type of operation, i.e., one in which anolefin is contacted with a catalyst slurry. When utilizing the controlmethod of this invention with this type of process, it has been found tobe desirable to operate at a temperature such that the polymer issubstantially all in solution in the hydrocarbon solvent. Thistemperature will vary according to the particular solvent which isu-tilized, e.g., with parafiins between labout 250 and 450il F., andwith naphthenes between about 230 and 450 F. However, it is to beunderstood that the method can be used with processes carried out attemperatures such that .the polymer produced is in v undissolved solidform.

Suitable solvents for use in the above described process arehydrocarbons which are liquid and chemically inert under the reactionconditions. Solvents which can be employed advantageously includeparatiins, such as those having from 3 to l2, preferably from 7 to 9,carbon atoms per molecule, for example, 2,2,4-trimethylpentane(isoc-tane), normal hexane, normal decane, the like. Another class ofsolvents which can be employed are naphthenic hydrocarbons having from 5to 6 carbon atoms in a naphthenic ring and which can be maintained inthe liquid phase under the polymerization conditions. Examples of suchnaphthenic hydrocarbons include cyclohexane, cyclopentane,4methylcyclopentane, methylcyclohexane, ethylcyclohexane, the methylethyl cyclopentanes, the methyl propyl cyclohexanes, and the ethylpropyl cyclohexanes. The described class of naphthenic hydrocarbonsincludes condensed ring compounds such as deoalin and the alkylderivatives thereof. A preferred subclass of naphthenic hydrocarbonswithin the above defined general class comprises those naphthenichydrocarbons having from 5 to 6 carbon atoms in a single ring and from 0to 2 methyl groups las the only substitu-- ents on the ring.r Thus, thepreferred naphthenic hydrocarbon solvents are cyclopentane, cyclohexane,methylcyclopentane, methylcyclohexane, the dimethylcyclopentanes, andthe dimethylcyclohexanes.

Referring now to FIGURE 1 of the drawing, there is shown a flow diagramwhich illustrates diagrammatically a preferred embodiment of the controlsystem. `While the invention is described in conjunction with aparticular polymerization process, it is to be understood that it is notintended to so limit the invention. The invention is applicable to anypolymerization process in which the material to be polymerized andcatalyst are continuously supplied to a polymerization reaction zone.

As shown in FIGUREl, a suitable solvent, such as cyclohexane, enters apolymerization reactor 30 through' an inlet conduit 31 at a temperatureof 234 F. This solvent enters the system at a rate of 237,000 pounds'perday and has a composition in weight percent as follows:

Methane Trace Ethylene 0.86 Ethane i 0.07. Cyclohexane 99.07

A feed material, such as ethylene, enters reactor 30 through an inletconduit 32 at a temperature of 260 F. This feed enters the system at arate of 34,113 pounds per day and has a composition as follows:

A catalyst enters reactor 30 through an inlet conduit 33. In theparticular reaction referred to by way of example,

isopentane, and

the catalyst is added to the system in the form of a slurry in thesolvent, 96% cyclohexane and 4%--catalyst. This catalyst is a chromiumoxidej-silica-alumina catalyst prepared by impregnating a Weight percentsilica and 10 weight percent aluminum gel composite with chromiumtrioxide which is dried and heated in air to form a compositioncontaining approximately 2.5 Weight per.-` cent chromium in the form ofchromium oxide, of which approximately one-half is in the form ofhexavalent chromium. The catalyst is added atthe rate of 2,725 pounds:of slurry per day.

Reactor 30 is surrounded by a jacket 34 through which a coolant iscirculated` A coil of heat exchangetubes 35 is disposed within theinterior` of reactor 30. Cooling coil 35 and jacket 34 thus provide ameans for removing heat` i from reactor 30 during the polymerization.Reactor 30 is provided with a stirrer 36 which is driven by a motor 37.Motor 37 is energized from a source of electrical energy, not shown,which is connected to the motor by means of a cable 38. The `reactoreuent is withdrawn through a product conduit 40. This etuent,`comprising a mixture of polymer, solvent,'spent catalyst and unreactedethylene, is subsequently passed to suitable separation means to recoverthe desired polymer.

The reaction mixture in reactor 30 is maintained at a desiredtemperature by circulating a coolantthrough jacket 34 and coils 35. Itis desirable to employ the same material, cyclohexane, for the coolantas is employed for the solvent. This eliminates any additionalseparating. problems if leakage should occurebetween the coolant conduits and the interior of the reactor. The coolant is introduced intothe system through an inlet conduit 41 which communicates with jacket 34.and coils 35.` The coolant is subsequently removed from the systemthrough a conduit 42 which communicates with a flash 4tank 43. Vapor isremoved from flash `tank 43 through `a conduit 44 which communicateswith the inlet of a condenser` 45.. The condensed vapors are returned totank 43- through 1 a conduit 46. The liquid in tank 43 isreturned toreactor` 30 through conduit 41.l In order to simplify the drawing, thevarious pumps and valves and other controllers necessary to establishand control the flows of materials have been deleted.

From an inspection of FIGURE 1, it should be evident that heat is addedto and removed from reactor 30 in several ways. The total heat liberatedby the polymerization reaction is computed.v This computation is madelby subtracting the heat which enters the reactor lfrom the heat which iswithdrawn from the reactor. The amounts of these heats are obtained bysumming a series of equations which represent the heat transferred intoand `out of reactor 30.

The first source of heat removal from reactor l30 re-Y sults from thesolvent supplied by conduit 31. This heat Q1 can be calculated from thefollowing equation:

The heat Q2 removed from the reactor by the coolant is represented asfollows:

cpm/Tgcom (2) where K2=an orifice constant AP2=pressure differentialacross an orifice in conduit 41 ATc=temperature difference, definedhereinafter, see

FIGURE 2 C3=specific heat of the coolant The sensible heat Q3 removed bycooling of the condensed vapors from ash tank 43 is represented asfollows:

Heat is also removed from reactor 30 due to conduction through theinsulated walls of the reactor. This heat loss Q4 can Ibe represented asfollows:

Q4=K4V (4) where K4=a constant V=temperature difference across reactorWalls.

The major amount of heat removal results from the heat of vaporizationof the coolant. This is represented as follows:

K3=an orifice constant AP3=pressure differential across an orifice inconduit 46 C5=heat of vaporization of the coolant at T1 2=heat ofvaporization temperature coefficient v=temperature of vapor in tank 43.

The heat Q6 removed from the reactor by the olefin stream is representedas follows:

Q6=F10W (C7) ATE (6) where 2 Flow=1low of the olefin C7=specic heat ofthe olefin ATE=temperature difference, defined hereinafter,

see FIGURE 2.

Heat is generated within the reactor by rotation of stirrer 36. Thisheat Q8 is represented as follows:

where K WLoad=energy supplied to motor 37 without a load on the stirrerKWNa Ld=energy supplied to motor 37 with a load on the stirrer3,413=B.t.u. per kw. hour.

'I'he heat Q7 removed by the catalyst slurry is assumed to be constant.Heat is also supplied to reactor 30 due to the heat of solution of theolefin in the solvent. This is represented as follows:

Q9=F10WXKG where: K6=constant relating to heat of solution.

The Various quantities indicated in -the foregoing equations aremeasured by the apparatus illustrated schematically in FIGURE 1. Thetemperatures of the materials flowing through conduits 31, 32, 41 and 46are measured by temperature sensing elements TS, TE, TC and TM,respectively. The tem-perature within reactor 30 is measured by atemperature sensing element TR. The temperatures of the liquid and vaporin tank 43 are measured by respective temperature sensing elements TFand Tv. The heat loss throng-h the reactor Walls is measured by asensing element L. The heat generated by stirrer 36 is measuredin termsof the power supplied to motor 37. This power is measured by a wattmeterKW which can be a thermal converter of the type described in Bulletin77- 39-0-2 of Leeds & -Northrup Company, Philadelphia, Pa., for example.The flow rates through conduits 31, 41 and 46 are measured in terms ofpressure differences across orifices in the respective conduits. Thesepressure measurements are made by respective detecting elements AP1,AF2, and AP3. The outputs of the several detecting elements of FIGURE lare applied -to a computer 48. The output signal of computer 48energizes a controller 49 which regulates either a valve 50 in conduit33 or a valve 511 in conduit 32. The rate of addition of catalyst orolefin to reactor 30 can thus be regulated to maintain the reaction at auniform rate, as evidenced by a constant heat output, so as to provide aproduct having uniform properties.

The Various temperatures which are measured by the apparatus of FIGURE 1can be conveniently obtained by means of thermocouples. These variousthermocouples are illustrated schematically in FIGURE 2. Certain ofthese thermocouples are provided with cold junctions which are indicatedby primed reference characters. Two separate thermocouples are employedto measure the temperature within reactor 30. These thermocouples aredesignated as TR and TR1. The terminals of t-hese various thermocouplesare connected in the manner illustra-ted in FIGURE 2 to provide thevarious quantities indicated adjacent the respective terminals which aredesignated 5a and 5b, 2a and 2b, 3a and 3b, 13a and 13b, 12a and 12b, 9aand 9b, 8a and 8b, and 6a and 6b. The three differential pressuremeasurements are applied in sequence 4to a flow transducer 55 whichprovides an output representative of ow. The output of transducer y55 isconnected between terminals 4a and 4b, 7a and 7b, and 10a and 10b. Thehea-t loss through the reactor walls is measured by a series of spaceddifferential thermocouples L having first junctions near the inner Wallsand second junctions near the outer walls. The outputs of thesedifferential thermocouples thus provide signals which are representativeof the heat transferred through the reactor walls. This signal isapplied between terminals 11a and 111b. The output signal of WattmeterKW is applied between terminals 14a `and 14b. The output signal ofiiowmeter 4U, which provides a signal directly related to ethylene ow,is applied Ithrough a transducer 56 to terminals 15a and 15b. As willbecome apparent from the detailed description which follows, the severaloutput signals from the apparatus of FIGURE 2 are all direct currentvoltages. These voltages constitute the inputs to the computer.

In the described example, TE, Ts, Tv, TF, TM, TR and TC areapproximately 260 F., 234 F., 230 yF., 228 F., F., 280 F. and 229 F.,respectively, KWLDad is 35 Ikw. and KWNo Load is 5 kw. Reactor 30 has avolume of 3300 gallons.

The detecting elements APl, AP2 and AP?, provide output alternatingcurrent signals which are representative of the pressure differencesacross the respective orifices. Suitable elements for this purpose aredescribed in Bulletin A-707, The Swartwout Company, Cleveland Ohio.These signals are converted by flow transducer 55 into direct voltageswhich are proportional to the respective flows. With reference to FIGURE3, the first output terminal of flow detecting element AP3 is connectedto the first end terminal of potentiometer 61. The second ou-tputterminal of detecting element APa is connected to the sceond endterminal of potentiometer 6\1 and to 7. ground. The contacter ofpotentiometer 61 is connected to a terminal 62 which is adapted to beengaged by a switch 63. Switch 6-3 is actuated by a yrelay 64. Flowindicating elements AF2 and AP1 are likewise connected across respectivepotentiometers 65 and 66. The contactor of potentiometer 65 is connectedto a terminal 67 which is engaged by switch 63 when relay 64 isenergized. The contactor of potentiometer 66 is connected to a terminal68 which is engaged by a switch 69 when relay 64 is not energized.Switch 63 is connected to a terminal 70 which is engaged by a switch 71when a relay 72 is not energized. Switch 69 is connected to a terminal73 which is engaged by a switch 74 when relay 72 is energized. Switches711 and 74 are connected to the first input terminal Iof an alternatingcurrent amplifier 75, the second input terminal of which is connected toground. Potentiometer 65 actually is not required in the specificexample described, and can effectively be eliminated by moving `itscontactor to the uppermost position.

Relays 64 and 712 are energized selectively by a circuit described indetail hereinafter. When both relays 64 and 72 are deenergized,potentiometer 61 is connected to its amplifier 75. When relay -64 aloneis energized, potentiometer 65 is connected to vamplifier 75. When relay72 alone is energized, potentiometer 66 is connected to anlplifier 75. Areference voltage is connected to amplifier 75 when 64 and 72 areenergized. The potentiometers 61 and 66 are employed to multiply thepressure difference signals by density correction factors.V

The first output terminal of amplifier 75 is connected through acapacitor 76 to the first end terminal of the primary winding of atransformer 77. The second output.y

terminal of amplifier 75 is connected to ground and to the second endterminal of the primary Winding of trans-VV former 77. VThe endterminals of the secondary windings of transformer 77 are connected t-othe control grids of triodes 78 land 79, respectively. The center-tap ofthe secondary winding of transformer 77 is connectedto ground. Aresistor 81 is connected in parallel with the secondary winding oftransformer 77. The anodes of triodes 78 and 79 are connected to aterminal 8-2 which is lmaintained at a positive potential. The cathodesof triodes 78 and 79 are connected to ground through respectiveresistors 83 and 84.. A source of alternating current 85 of the samefrequency as the output signals from elements API, AP2 and AP3 isapplied across the primary winding of a transformer 86. The first endterminal of the secondary winding of transformer 86 is connected.

through capacitors 87 and 88 to the cathodes of triodes 78 and`79,-respectively. The second end terminal of the secondary winding oftransformer 86 is connected 4to ground. The cathode of triode 79 isconnected through series connected resisto-rs 90 and 91 to the firstinput terminal of a direct current amplifier 92.: The cathode of 'triode78 is connected through series connected resistors 93 and 94 to thesecond inputterminal of amplifier 92. A capacitor 95 is connectedbetween ground and the junction between resistors 90 and 91 and acapacitor 96 is control grid of a triode 132. Switch `128 is connected`lthrough a capacitor 133 and a resistor 134 to the anode connectedlbetween ground and the junction between resistors 93 and 94.

Triodes 78 and 79 .and the circuit elements associated therewith thusform a phase sensitive detector which provides an output directV voltageof magnitude proportional to the alternating input voltage. The outputsignals from the cathodes of the two tubes are filtered so that a smoothdirect voltage is supplied to the input of amplifier 92.4 The remainderof the circuit illustrated in FIGURE 3 with the exception of elements.250 to 253' is provided to obtain a signal proportional to .the squareroot ofthe output signal from amplifier 92.

The first output terminal of amplifier 92 is connected -through aresistor 100, a variableV resistor 101, a resistor 102 and a capacitor103 to .the control grid of a triode 104. The control grid of triode 104is connected to a negative potential terminal 108 through a resistor117.

Resistor 101 is shunted by a nonlinear resistance `ele-` ment 105. Thecathode of triode 104 is connected to the cathode of a triode 106. Thesetwo cathodes are con-` nected through a resistor 107 to a terminal 108which `is` through a resistor 113. The cathode of triode 111 iscon`nected to the ground through a resistor 114 which is shunted by acapacitor 115. The .anode of triode`111 is connected to terminal 109through a resistor 116.` The cathode of triode 111 is also connected tothe cathode of a triode 118 through a resistor 119. The anode of triode118 is connected to terminal 109, and the cathode `of triode 118 isconnected through a resistor 120 to terminal` 108.` The cathode oftriode 118 is connected to ground through a potentiometer 121. Thecontactor of poten.

tiometer 121 is connected to output terminals 4a, 7a, and 10a. Thecathode of triode 118 is also connected to the junction between resistor102 and capacitor 103" through a resistor 122 and a second nonlinearresistance elejment 123.

Triodes 104, 106 and 111 and the circuit elements asso-` ciatedtherewith thus provide an operational amplifier wherein the outputsignal is a functionl of the square root of the input signal. This isaccomplished by means of'the nonlinear resistance elements in the input`circuit -and` in the feedback circuit. These elements are selected so`that the current fiows therethrough are anrinverse y.ex-

` Vponential function of the voltages appliedacross the eley ments.

A stabilizing :amplifier is provided in `the circuit of FIGURE 3 toavoid drift in the direct current operational amplifier. The junctionbetween resistor 102 ,Wand capacitor 103 `is connected through aresistor 125 Ito the rst contact 126 of ,a vibrator assembly. The secondcontact 127 is connected to ground. VA. switch 128 vi-4 brates betweencontacts 126 and 127 when a coil 129` is energized by a source ofalternating current 130. Contact 126 is connected through .a capacitor`131 to the of a triode 135. The anodes of triodes 132 and 135 areconnected through respective resistors 136 and 137 to a terminal 138ywhich is maintained at a positive potential. The cathodes of triodes132 and 135 Aare connected to ground through respective resistors 140and 141. The control grids of triodes 132 and 135 are connected `toground through respective resistors 142` 2and 143. The

anode of triode 132 is connected through a capacitor 144 t to theVcontrol grid oftriode `135.y A capacitor 145 is connected kbetween theanode of triode 132 and ground.

Switch 128 is also connected through a resistor 146 to the control gridof triode 106. The control gridfof triode` grid of triode 118 isconnected to terminal 108 through 'n a resistor 154.

The alternating current amplifier thus formedby triodes l 132 and 135forms a feedback network in the direct .cur-

rent amplifier in order to stabilize the directcurrent arnplifieragainst drift. l

The direct voltages which appear between lthe several pairs of terminalsof FIGURE 2 are converted into `corresponding potentiometer settings inorder to perfor-mV the multiplications required to solve the heattransfer. equa-tions.

These voltages are converted into the respecy 'tive potentiometersettings in sequence and repetitively by means of a stepping switch. Thecircuit employed to 9 establish the potentiometer settings isillustrated schematically in FIGURES 4 and 5. The output terminals ofFIGURE 2 are represented in FIGURE 4 as the a and b terminals of thestepping switch The a terminals are engaged in sequence by switch arm Aand the b -terminals are engaged in sequence by switch arm B. The switcharms move between adjacent terminals each time a solenoid 150 isenergized. The stepping switch preferably is -of the rotary type so thatthe switch arms move successively to adjacent contacts and then repeatthe operation. The stepping switch employed in one particular embodimentof this invention had contacts associated with each switch arm. Thecomputing operation of the described example can be accomplished withless contacts, although some of the additional contacts are employed inthe calibration steps described hereinafter.

Switch arm A is connected to a terminal 151 which is engaged by a switch152 when a relay 153 is deenergized. Switch arm A is also connected to aterminal 154 which is engaged by a switch 155 when a relay 156 isdeenergized. Switch 155 is connected through a resistor 157 to switcharm D of the stepping switch. Switch arm B is connected to a terminal158 which is engaged by switch 159 when relay 153 is deenergized. Aresistor 404 and a capacitor 405 are connected in parallel betweenswitch arm B and ground. Switch armB is also connected to a terminal 161which is engaged by a switch 162 when relay 156 is deenergized. Switch162 is connected to a terminal 164 which is engaged by switch 165 when arelay 166 is deenergized. Switch 165 is connected to the first inputterminal of servo amplifier 168. The second input terminal of amplifier168 is connected to switch arm C of the stepping switch. A capacitor 169is connected between terminal 164 and switch arm D. The first outputterminal of amplifier 168 is connected to a terminal 170 and to a switch171 which engages a terminal 172 when a relay 173 is energized. Terminal172 is connected to the first 'input terminal of a servo motor 174. Thesecond output terminal of amplifier 168 .and the second input terminalof motor 174 are grounded.

Terminals 1c and 2c of the stepping switch are connected to a terminal176; terminals 1e and 2e are connected to a terminal 177; terminals 1fand 2f 4are connected to a terminal 178; .and terminals 1d and 2d areconnected to a terminal 179. A variable resistor 180, a resistor 181,and a battery 182 are connected in series relationship between switcharms E and F. A resistor 183 and a standard cell 184 are connected inseries relationship between switch arm E and a terminal 185 which isengaged by switch 165 when relay 166 is energized. Terminals 176, 177,178 and 179 areconnected to the circuit illustrated in FIGURE 5.Terminal 176 is connected to the junction between resistors 180' and181'. The second terminal of resistor 180' is connected to termina-l178, and the second terminal of resistor 181 is connected to terminal177. A resistor 183', a potentiometer 184', and a resistor 185 areconnected in series relationship between -terminals 178 and 177.Resistors 186 and 187 are cionnected in parallel with the potentiometer184. Terminal 179 is connected by means of a conductor 188 which forms atemperature compensating thermocouple cold junction, to the contactor ofpotentiometer 184.

Terminal 170 of FIGURE 5 is connected to a switch 190 which engages aterminal 191 when a relay 192 is energized. Terminal 191 is connectedthrough the first coil 193 of a reversible two-phase induction motor 194to ground. One terminal of the second coil 195 of motor 194 is connectedto a terminal 196. The second terminal of coil 195 is connected to aterminal 197 which is engaged by a switch 198 when relay 192 isenergized. Switch 198 is connected to a terminal 199. An alternatingcurrent source described hereinafter is connected between terminals 196and 199. The drive shaft of motor 194 is connected to the contactor ofpotentiometer 184'.

The drive shaft of motor 194 is also connected to the contactors ofpotentiometers 201 and 282.

The circuit of FIGURES 4 and 5 forms a self-balancing potentiometer. Theinput signal appears betweenl the first input terminal of amplifier 168and switch arm D. This signal is balanced against a reference voltage inthe bridge network so that any potential difference energizes motor 194through amplifier 168. This portion of the circuit of FIGURES 4 and 5comprises a conventional balancing circuit of the general type describedin Bulletin No. `B15-13, Minneapolis-Honeywell Regulator Co., BrownInstrument Division, Philadelphia, Pa. If the input signal differs fromthe reference voltage, motor 194 is energized to adjust the position ofthe contactor of potentiometer 184. This adjustment continues until thecircuit is restored toa set of balance. The rotation of motor 194required to establish this balance is, therefore, a function of themagnitude of the input signal. This rotation also establishes thepositions of the contactor of potentiometer 201.

The computer of this invention is also provided with thirteen additionalnetworks, not shown, of the general form of FIGURE 5. The first of theseadditional networks is lconnected into the circ-uit of FIGURE 4 by meansof terminals 176', 177', 178 and 179. The last `of these additionalnetworks is connected into the circuit of FIGURE 4 by means of terminals176n, 17711, 17811, and 179:1. The potentiometers of these fourteennetworks are adjusted sequentially as the arms of the stepping switchmove to adjacent contacts. This entire stepping operation is repeatedcontinuously to reset the potentiometers representative of changes inthe Variables to be measured.

One of the networks employed to perform the multiplication required tosolve the heat transfer equations indicated above is illustrated inFIGURE 7. A source of alternating current 205 is connected across apotentiometer 206. This primary Winding of a transformer 207 isconnected between the contactor and Vone end terminal of potentiometer206. The secondary winding of transformer 207 is connected across apotentiometer 201:1. A potentiometer 208, having a grounded center tap,is `connected across the secondary winding of transformer 207. Thecontactor of potentiometer 201a is connected to the first input terminalof an isolation amplifier 209. The first -output terminal of amplifier209 is connected to the first end terminal of a potentiometer 201b. Thesecond end terminal of potentiometer 201b is connected to ground. Thecontactor :of potentiometer 201b is connected to the first inputterminal of 1an isolation amplifier 210. The first ouptut terminal ofamplifier 210 is connected to the first end terminal of potentiometer201C. The second end terminal of potentiometer 201e` is connected toground. The `contactor of potentiometer 201e` i-s connected to the firstinput terminal of an amplifier-211.

The first output terminal of amplifier 210 is` connected an 'outputterminal 212a. The second output and input terminals of amplifiers 209,210 and 2 11 are connected to ground.

With reference to Equation 1, it can be seen that there are'threeprincipal quantities to be multiplied to obtain the product. These threevariables are represented by the three potentiometers 20111, 201b and201e of FIGURE 7, each of which corresponds to one of the potentiometers201 of FIGURE 5. The indicated multiplication is provided by these threecascade connected potentiometers. The isolation amplifiers are employedto prevent current from being drawn from lthe potentiometers. Circuitssimilar to the circuit of FIGURE 7 are provided for each of the otherheat transfer equations to be solved. The equations which have fewerthan three variables to be multiplied require fewer potentiometers.'Ihese circuits are otherwise similar to the circuits of FIGURE 7.

The output signals of the plurality of multiplying circuits of the formof FIGURE '7 are applied to terminals 1l 212a, 212b 212i of FIGURE 8.These .terminals are connected through respective resistors 213a, 213b,213i to the first input termina-l of a summing amplifier 480. The firstoutput terminal of amplifier 480 is connected through a capacitor 214 to`the first input terminal of a recorder-controller 215. The second inputterminal of controller 215 is connected to ground. The signal applied tocontroller 215 represents the amount 4of heat liberated by thepolymerization reaction. This is obtained from the addition of 'the heattransfer equations, plus or minus depending upon whether heat is addedor substracted. This signal is lapplied through a conventional controlmedium to regulate either valve 50 orlvalve 51. If the indicated heat ofreaction should increase, the rate of addition of olefin or catalystk tothe reactor is decreased.l If the indicated heat of reaction shoulddecrease, the flow of olefin or catalyst is increased. It is thuspossible to maintain the lreaction at a steady rate which resultsin theproduction of polymer of uniform quality. Thiscontrol operation isdescribed,

by a source of alternating current 225.' Contacts 222 and 223 areconnected to the respective end terminals of the primary winding of atransformer 226. TheA second inputterminal 227 (connected to switch C ofFIGURE 4) of amplifier 168 is connected to the center tap of the primarywinding of transformer 226. The first end terminal'of the secondarywinding of transformer 226 is connected to the control grid -of atriode228. The second end terminal of the secondary winding oftransformer 226 is connected to ground. A capacitor 229 is connected .inparallel with the secondary winding of transformer 226. The cathode oftriode 228 is connected. to ground through a resistor 230 which isshunted by capacitor 2311 The anode of triode 228.is connected throughresistors 232 and 233 to aterminal 234 which is maintained at a positivepotential. A capacitor 235 is connected between ground and the junctionbetween resistors 232 and 233. The anode of triode 228 is also connectedthrough a capacitor 236 to the lfirst end terminal of potentiometer237.v The second end terminal of potentiometer 237 is connectedtoground. The contacter of potentiometer 237 is connected to the controlgrid of a triode 238. The cathode of triode 238 is connected to groundthrough a resistor 240. The anode of triode 238 is connected to terminal234 through la resistor 241. The anode of triode 238 is also connectedto ground through a capacitor 242 and resistors 243, 244, 245, 246 and247 which are connected in series relationship.

The circuit thus far described in FIGUREI 6 converts a direct currentinput signal into an alternating signal which is amplified. The voltagedividing network formed by resistors 243, 244, 245, 246 and 247 permitsoutput signals of different amplitudes to be applied to the individualservo motors. This cornpansates` for input signals of dierentamplitudes. In one particular `computer which has been constructed, theoutput circuit from the.

Avoltage dividing network was of the configuration illustrated in FIGURE6. The output terminals 1g, 2g 16g of the stepping switch are connectedto the indicated points on the voltage dividing network.

Switch arm G is connected to the control grid of triode 250. The cathodeof triode 250 is connected to ground through a resistor 251 which isshunted by a capacitor 199 energize servo motor 194 of FIGURES. ThecenterA tap of the secondary winding of transformer 260 is connected toa switch 265 `which 'engages -a terminal 266 when a Vrelay 267 isenergized. Terminal 199 is connected to a switch 268 which engages aterminal 269 when relay 267 is energized. Terminal 266 isconnectedthrough.

the first winding 270 of two-phase induction motorf174 to ground.Terminal 269 is connected through the second winding 271 of motor 174 tothe first terminal of current source 261. Y

The output signal of i the motor drive amplifier` of FIGURE 6 thusenergizes one of the servo motors194 of FIGURE 5 when a relay 192 ofFIGURE 5 is energized. The standardization motor `174 is actuated when;relay 267 is energized. A single servo amplifier thus ener-` gizes aplurality of motors in sequence` to perform the balancing operations andstandardizing functions.

The stepping switch employed .to establish the variables in sequence isactuated by the circuit illustrated in the.`

lower portion of FIGURE 6. The cathodes of triodes 256 and 257 areconnected through a resistor 280 to the 1 control grid of a triode 281.A capacitor 282 is f connected between the control grid of triode `'281and ground. The cathode of triode-281 is connected toV ground through aresistor 283, and the anode of triode 281` is connected to a positivepotential terminalr 284 through a resistor 285. The anode oftriode 281is also connected to the first end terminal of a potentiometer 286,-thesecond end terminal of potentiometer 286 being connected to a negativepoten tial terminal 287.

The contactor of potentiometer `286 is connected di-I `rectly to the`control grid of va triode 288` and through a resistor 290 to the controlgrid of a triode 291. Thecathodes of triodes 288 and 291 :are connectedto ground.

The anodes of these triodes are connected to terminal 284 through aresistor 292.1 The anodes of triodes 288 and 291` are also connectedthrough a resistor 293 to the conis connected through a resistor 295 toYnegative potential terminal 287. The cathode of triode 29.4 is connecteddirectly to ground, and the anode of triode 294 is connected through aresistor 296 to positive potential terminal 284. The anode `of triode-294 -is also connected through a capacitor 297 `to the control grid 0ftriode V291.

The anode of triode 294 is connected to a terminal 300 which normally isengaged by a switch 301.1 Switch i301 trol grid of a triode 294. Thecontrol grid .of triode 294 is connected throughseries` connectedresistors 302 `and 303 to negative potentialterminal 287. The. junctionlbetween these resistors is connected,4 to terminalsV 1h, 2h 151i. Theseterminals Vare engaged by switch arm H of the stepping switch. Switch301 is Valso adapted to engage a terminal 304 which is connected to aswitch 305.

Switch 305 normally engages a terminal 306 which is conl nected througha resistor 307 to positive potential terminal 284. Switch 305 can alsoengage .a terminalr 308 l which is connected to ground. l. Switch arm His connected through a resistor 310 to the control grid of the triode3111.vvv

Thecathode oftriode 311 is connected to ground, and the anodeV of triode311 is. connected through a vresistor 312 to positive potential terminal284. The .anode of triode 311 is lconnected through neon lamps 313, 314and 315 and a resistor 316 to negative potential terminal.287.f VThejunction between lamp -315 and resistor 316 is connected I througharesistor 318 to the control grid` ofA a triode 319 and through aresistor 320 to the controlgrid of a triode 321. The cathodes of triodes319 and 321 are connected to ground. The anodes` of triodes 319 and 321are yconi3 nected to the first terminals of a resistor 322 and solenoid150. The second terminals of resistor 322 and solenoid 150 are connectedto the junction between a rectifier 333 and a capacitor 334. Currentsource 261 is connected across the primary winding of a transformer 336.The first end terminal of the secondary winding of transformer 336 isconnected through a resistor 337 to rectifier 333. The second terminalof the secondary winding of transformer 336 and the second terminal ofcapacitor 334 are connected to ground. A positive potential thus appearsat the junction between rectifier 333 and capacitor 334.

The anodes of triodes 319 and 321 are connected through series connectedresistors 340 and 341 to the control grids of triodes 256 and 257. Acapacitor 342 is connected in parallel with resistor 341. I'he junctionbetween resistors 340 and 341 is connected through a resistor 343 tonegative potential terminal 287.

Terminal 16h of the stepping switch is connected through a resistor 345to the grounded cathode of triode 294. Terminals 17h to 25h areconnected to a first interrupter contact 346 of the stepping switch. Theinterrupter switch 347 is connected through a resistor 348 to terminals17h to 25h. A capacitor 349 is connected in parallel with resistor 348.A resistor 350 is connected between terminals 17h to 25h and negativepotential terminal 287.

In order to describe the switching operation, it is assumed that theinput signal from one of the transducers is different from the signallast applied from this particular transducer. This results in thepotentiometer circuit being unbalanced so that the servo motor isenergized to restore a balanced condition. At this time there is arelatively small direct current through triodes 256 and 257. Thecathodes of these two triodes are thus maintained at a relatively smallpositive potential. This potential is inverted by triode 281 so that apotential is applied to the control grid of triode 288 which permitsthis triode to conduct. Conduction by triode 28S results in thepotential applied to the control grid of triode 294 being sufiicientlysmall to extinguish conduction by triode 294. This effectively applies apositive pulse to the control grid of triode 291 which causes it toconduct. Triodes 288 and 291 thus operate essentially in parallel. Thepotential at the anode of triode 294 is applied through the steppingswitch to the control grid of triode 311. The decreased potential at theanode of triode 311 is in turn applied to the control grids of triodes319 and 321 to keep these two triodes from conducting.

When the bridge circuit becomes balanced, the direct current throughtriodes 256 and 257 increases substantially to increase the potentialapplied to the control grid of triode 281. This results in the potentialat the control grid of triode 288 being decreased sufficiently toextinguish conduction by this triode. However, triode 291 continues toconduct until the original charge on capacitor 297 leaks off. Thisincorporates a delay, which can be of the order of one second, forexample. At the end of this period, conduction through triode 291 isextinguished so that the potential at the control grid of triode 294 isincreased. The resulting conduction by triode 294 results in thepotentials at the control grids of triodes 319 and 321 being increasedto cause conduction through these triodes. This energizes solenoid 150to cock the stepping switch. The resulting negative pulse at the anodesof triodes 319 and 321 is applied to the control grids of triodes 256and 257. This negative pulse reduces the potential of the two cathodesto restore the condition initially described. This initial conditionresults in conduction through triodes 319 to 321 being extinguished toenable the arms of the stepping switch to move to the next contacts.

The purpose of the delay in the multivibrator formed by triodes 288 and291 is to delay cocking of the stepping switch for a given time afterthe null signal level is reached at the cathodes of triodes 256 to 257.This insures that the potentiometer circuit reaches a final balancedcondition before the next variable is engaged by the stepping switch.The pulse fed back to the servo amplifier from triodes 319 and 321assures release of the stepping switch solenoid once it has been cocked.The interrupter switch 347 moves the stepping switch rapidly fromcontacts 17h to 25h and back to 1h. At position 16h, the control grid oftriode 311 is connected to ground through resistors 310 and 345. j

The several servo motors 194, as shown in FIGURE 5, are energized insequence by the associated relay 192 being energized. These relays areactuated by triodes 360a, 360b 36011 of FIGURE 9. The cathodes of eachof these triodes are connected to ground. The anode of triode 360a, forexample, is connected to a terminal 361a which is connected to the rstterminal of relay 192 of FIGURE 5, the second terminal of the relaybeing connected to a positive potential terminal 377. The anodes of theremaining triodes are likewise connected to a relay which energizes arespective one of the servo motors. The grids of triodes 360a, 360b 360nare connected to respective terminals 2z', 3i 151' of the steppingswitch. The control grids of triodes 360a, 360b 36011 are also connectedthrough respective resistors 362a, 362b 362n to the junction betweenresistors 364 and 365. A spare triode 3600 also is provided. The secondterminal of resistor 364 is connected to a negative potential 366, and asecond terminal of resistor 365 is connected to ground. A capacitor 367is connected in parallel with resistor 365.

A terminal 370 is connected to the secondary winding of transformer 336of FIGURE 6. Terminal 370 is connected through a resistor 371, arectifier 372, and a capacitor 373 to ground. The anode of a triode 374is connected through relay coil 267 to the junction between rectifier372 and capacitor 373. The cathode of triode 374 is connected to ground.The control grid of triode 374 is connected to terminal 1i of thestepping switch and to the control grid of a triode 375. The controlgrid of triode 374 is also connected to the junction between resistors364 and 365 through a resistor 376. The anode of triode 375 is connectedthrough relay coil 166 to the junction between rectifier 372 andcapacitor 373. The

cathode of triode 375 is connected to ground. Terminal 377 is connectedbetween rectifier 372 and capacitor 373.

The potentiometer circuit of the ycomputer is standardized when switcharm I engage-s terminal 11'. At this time triode 374 yconducts .so as toenengize relay 267, see FIGURE 6. This connects the output signal fromthe amplifier of FIGURE 6 to standardizing motor 174. Motor 174 thenadjusts resistor 180 of FIGURE 4 until there is a zero signal applied tothe input of amplifier 168. Relay 166 is also energized at this time sothat a voltage from standard cell v184 is applied to the input ofamplifier 168. This operation standardizes the potent1ometer cincuit ofFIGURE 4.

Each time the arms of the stepping switch move to the next contacts,interrupter switch 347 of FIGURE 6 momentarily engages contact 346. Thisapplies a positive pulse from terminal 380 of FIGURE 6 through acapacitor 381 to the control grid of a triode 382 of FIG- URE 9. Thecathode of triode 382 is connected to ground. 'I'he control grid oftriode 382 is connected to a negative potential terminal 390 through aresistor 383. The anode of triode 382 is connected through a resistor384 to a positive potential terminal 385.` The anode of triode 382 isalso connected through a capacitor 386 to the control grid of la triode387. The cathode of triode 387 is connected to ground. The anode andcontrol grid of triode 387 are connected to terminal 385 throughrespective resistors 388 and 389. The anode of triode 387 is alsoconnected through a resistor 391 to the control grid of triode 382. The-anode of triode 382 is connected through a resistor 392 to switch armI.

This circuit provides a pulse which maintains the motor relay triodes360 nonconductive for a predetermined time during and after movementl ofthe switch arms of the` l through relay 64 of FIGURE 3 to a positivepotential .terminal 438. 'Ihegrids of triodes 432 and 434 are con- Thecomputing circuit is also providedwith apparatus for checkingperiodically the operation of the transducers and of `the computeritself. With reference to FIG- URE 4, there is shown a plurality ofpotentiometers 400:1, 400b 4001 which are adapted to provide presetvoltages. The iirst terminals of all these potentiometers except 4000are connected to a negative potential terminal 401. The first terminalof potentiometer 400C is con-y nected ,tov a terminal 402 which isconnected to the cathode of triode 118 through a resistor 402', seeFIGURE -3. The second terminals of all these potentiometers areconnected to ground. The contactors of these potentiometers areconnected to the indicated k terminals of the stepping switch. Switcharm K is connected to a terminal 403. Switch 152 of FIGURE 4 isconnected lto a terminal 406 which is connected to the lcontrol grid ofa triode 407 in FIGURE 9. Switch `159 of FIGURE 4 is connected to aterminal 408 which is connected to the cathode of triode 407 ofFIGURE`9. Terminal 370 of FIGURE `9 is connected through arcapacitor410, an inductor 411 and a capacitor 412 to ground. The junction betweencapacitor 410 and linductor 411 is connected through a rectifier 413 anda resistor 414 to terminal 408. The junction between capacitor 412'andinductor` 411,is connected through a resistor r415 to terminal 406. Thejunction between capacitor 412 and inductor 41.11 is connected through acapacitor 417 to the junction between rectifier 413 and resistor 414. Apotentiometer 418, 'havin-g a grounded contactor, is connected betweenterminals 406 and 408. The anode of triode 407v is connected through aresistor 420 `to terminal 385. The anode of triode 407 is also connectedthrough resistor 421 and a neon lamp 422.to ground. The anode of triode407 is connected through a resistor 423 to a terminal 424 which isconnected through a resistor 423 to a terminal 424 which is connected tothe junction between resistors 302 and 303 of FIGURE.

During one portion of the checking cycle, relay 153 is deenergized sothat the signals between the a and b contacts of the stepping switch areapplied between the control grid and cathode of triode 407, FIGURE 9.This triode normally conducts. However, if an open circuit should Aoccurin the transducing elements, conduction by triode 407 lis extinguishedwhich increases the potential at the anode thereof. This increase inpotential causes.

neon lamp 422 to conduct so as to provide a warning signal. Theresulting positive pulse is also applied throughterminal 424 to the hcontacts of the stepping switch, FIGURE 6, to prevent the steppingswitch from moving further.-

The circuit which operates relays 153 and 156 of FIG- URE 4 and relays64 `and 72 of FIGURE 3 is illustrated in FIGURE 9. Switch arm J of thestepping switch is connected to a source of positive potential 430.`Ter,

minals 1]', 2j, 3j, and 4j are connected through a resistor 431 to thecontrol grid of a triode 432. Terminals 5j,

6j and 7j' are connected through a resistor 433 to the control grid of atriode 434. The cathodes of triodes` 432 and 434 are connected toground. The anode ofY .triode 432 is connected by a terminal 435 throughrelay 72 of FIGURE 3 to a positive potential terminal 436. The anode oftriode 434 is connected 'by a terminal 437 nected through respectiveresistors 440 iand 441 tto the junctionbetween resistors 364 and `365.`The control grids of tn'odes 432 ,and 434 are also connected throughrespective resistors 442 and 443 to the anode of a triode 445.: Theanode of triode 445 is connected through relay 153 of FIGURE 4 and aresistor 446 to a positive potential terminal 447. The anode of triode;445 is also connected through a capacitor 448 to the control grid of atriode 449. The lcathodes of triodes 445 and 449` are connected toground.l The anode of triode 449 is connected through relay l156 and aresistor 450 to terminal 447 and to terminal 19]'. Terminal 19j is alsoconnected to a negative potential terminal 451 through resistors 452 and453. A resistor 454 and a neon lamp4 455 are connected in seriesrelationship with one another and in parallel with resistors 450. A`resist-or 456 is connected ybetween the junction between resistors 452and 453 and the junction between resistor 450 and a relay 156. The anodeof trioder 449 is also connected through a capacitor 458 to the controlgrid of trio-de 445.1V

Terminal 16j is connected through a resistor 460 t0 the control grid oftriode 449. Terminal 25j is connected to ground through resistors 461and 462.1 A capacitory 463 .is connected between the control grid oftriode `449 and the junction between resistors 461 and 462. The.

control grid of triodel 449 is also connected to a switch 464. Switch464 is adapted to engage a terminal 465 t which is connected to thejunction between resistors 364 and 365 or a terminal 466 which isconnected to a switch after a relatively large number of cycles of thestepping switch. Conduction by triode 449 extinguishes conduction bytriode 445.` This energizes relay 156 `and `deenergizes relay 153. Underthis condition, the standard voltages from the potentiometers of FIGURE4 are connected in the `circuit in place of the voltages from thetransducers of FIGURE l. The outputsignal of the computer at this timeshould havea predetermined value in view of the standard input signals.Pulses generated atfposition 25j are coupled through capacitor 463 tothe grid of triode 449 to insure that the multivibrator flips atposition 25j'only and notdurintg normal scanning of the variables(positions 2 through l5).

This overall operation of the computer` is checked by means of thecircuit shown in FIGURE 8. The second terminals of resistors 213a, 213bV213i are connected to the rst input terminal of4 a summing ampliiierA.480 Iwhich is provided .with a feedback resistor `480a.` Thefirst-output terminal .of ampliiier 480 is connected through a resistor481 to the controlzgn'd `of a pentode 482.1 The second input and outputterminals of ampliiier` 480 are lconnected to ground. The control gridof pentode 482 i-s connected to ground through a variable resistor 483.`The cathode` and suppressor grid of pentode 482 `are connected` `toground through` a resistor; 484 which is shunted lby a capacit-or 485.'The anode ofpentode 482 is connectedthrough a resistor 486 to a terminal487 which is maintained ata positive potential. The screen grid ofpentode 482 is connected to terminal 487 through 17 terminal .of thesecondary winding of transformer 492 is connected to ground through apotentiometer 493. The second end terminal of the secondary winding oftransformer 492 is connected to ground. @The contacter of potentiometer493 is connected through a capacitor 494 and a -resistor 495 to thecontrol grid of pentode 482. The junction between capacitor 494 andresistor 495 is connected to ground through a resistor 496.

The anode of pentode 482 is connected through a capacitor 500 to thetirst end terminal of a potentiometer 501. The second end terminal ofpotentiometer 501 is connected to ground. A capacitor 502 is connectedbetween the anode of pentode 482 and ground. The contactor ofpotentiometer 501 is connected to the control grid of a triode 503. Theanode of triode 503 is connected to terminal 487 through a resistor 504,and the cathode of triode 503 is connected to ground through a resistor505 which s shunted by` a capacitor 506. The

ranode of triode 503 is connected through a capacitor 50-7 to thecontrol grid of a triode 508. The control grid of triode 508 isconnected to ground through a resistor 509. 'Ihe cathode of triode 508is connected to ground through a resistor 10, and the anode of triode508 is connected to terminal 487 through a resistor 511.

The sum of the voltages from the several multiplying units of FIGURE 7is thus applied `to the control grid of pentode 482. A reference signalwhich is 180 out of phase with this summed signal is also applied to thecontrol grid of pentode 482 from current source 205. 'Ihe magnitude ofthe diterence between the output and reference signals -at junction of481, 495 and 483 can `be varied by adjustable resistor 483 to determinethe magnitude of the permissible error. 1f the overall computer networkis operating properly with the reference voltages being applied .to theinput terminals, the output signal from pentode 482 is zero. However, ifan error has occurred any place in the computer network, the twovoltages being compared .are no longer equal so that an output sign-a1is provided by pentode 482. The amp-lidier circuit formed by triodes 503and 508 is biased so that the output signal 'from triode 508 neverexceeds a predetermined value, that is, the amplier output is clipped.

The circuit shown in the remainder of 8 forms a multivibrator whichnormally provides output pulses at a predetermined frequency duringoper-ation of ,the computer. The cathodes of trlodes 513 and 514 areconnected to ground. 'Ihe anode of triode 513 is connected to terminal487 through a res-istor 515, and the anode of triode 514 is connected toterminal 487 through resistors 516 and 517. The control grid of triode51,3 is connected to terminal 487 through a resistor 51'8. A capacitor519 is connected between the anode of triode 514 and the cont-rol gridof triode 51'3. A capacitor 520 is connected between the anode of.triode 513 and the control grid of triode 514. The control grid oftriode 514 is connected to a switch 521 which is adapted to engageterminals 522 and 523. Terminal 523 is connected to ground through aresistor 524. The checking circuit of FIGURE 8 is turned oft when switch521 engages terminal 523. Terminal 522 is connected through a resistor525 to the contactor of potentiometer 526.` The first end terminal ofpotentiometer 526 is `connected through la resistor 527 to a negativepotential terminal 528. The second end terminal of potentiometer 526 isconnected through a resistor 529 to -a terminal 530 which is connectedto the anode of triode 449 of FIGURE 9.

During normal operation of the computer, the bias applied to the controlgrid of triode 514 from potentiometer l526 is such that themultivibrator `formed by triodes 513 and 514 provides an output pulse atpredetermined intervals, which can be of the` order of one-half second,for example. The junction between resistors 516 and 517 is connectedthrough a capacitor 532 `to a terminal 533 which is connected toterminal 16h of FIGURE 6. The resulting pulses move the stepping switchpast the 16th 18 contacts. The anode of triode 508 is connected througha capacitor 535 to the positive terminal of a rectitier 536 and to thenegative of a rectifier 537. The positive terminal of rectitier 537 isconnected to ground. The ne-gative terminal of rectitier 536 isconnected to ground through a resistor 538 which is shunted by acapacitor 539. An output signal from triode 508 thus results in anegative signal appearing at the control grid of triode 514. When triode449 of FIGURE 9 is conducting, this signal from triode 508 extinguishesconduction through triode 514 so that the pulses 'applied to terminal16h of FIG- URE 6 are discontinued. This operates to stop furthermovement of the stepping switch. The circuit of FIG- UIRE 3 is checkedwhen relays 64 and 72 of FIGURE 3 are both energized. This connects theinput of ampli-tier 75 to the contactor of a potentiometer 250. One endterminal of potentiometer 250 is connected to ground. The second endterminal of potentiometer 250' is connected through a variable resistor251 and a resistor 252 to the iirst end terminal of the secondarywinding of transformer 86. A capacitor 253 is connected in parallel withresistor 252'. A reference check voltage is thus applied from source tothe input of amplier 75.

It `should be evident from the foregoing description that many of theterminals shown are lmerely for the purpose of designating connectionsbetween the several -gures. Also, many of the switches are for thepurpose of turning oit portions of the apparatus or to permit manualoperation for test purposes.

The circuit illustrated normally provides an automatic computation ofthe heat liberated by the polymerization reaction. The sources of heatremoval from the reactor are indicated as signals of 4a lirst polarityWhereas the sources of heat addition are indicated as signals of asecond polarity. The sum provided by the circuit of FIGURE Sthusrepresents the net heat of reaction. This final signal is analternating voltage. Controller 2-15 converts this signal into an outputcontrol signal, such as a pneumatic pressure which regulates valve 50 orvalve 51 of FIGURE 1.l 'This can be accomplished by a transducer of thetype described in Bulletin A-7=1 0, .the Swart- Wout Company, Cleveland,Ohio. In one speciiic embodiment of the control system, valve 50 can berepresented by a variable stroke piston pump to pass the catalystslurry. IThe control signal can adjust the stroke or vspeed of the pump.A conventional control valve can also be employed for this purpose. Thisinvention thus provides an `eilicient procedure for regulatingpolymerization in response to a measurement of the heat liberated by thereaction. |It should be evident that in some polymerization systems,certain of the variables measured in the example normally aresuiiciently const-ant asto be omitted. The control system can thus besimplified in these appli-cations.

In the computer thus yfar described it has been assumed that thetemperature of reactor v30 does not fluctuate rapidly, for example, notmore than about 0.'1 E per minute. However, it has been found inpractice that the reactor temperature sometimes changes at a fasterrate. The circuit illustrated in FIGURE 10 is provided to compensate forsuch ch-anges in reactor temperature. A thermocouple TR is employed tomeasure the temperature of reactor 30. The output signal of thisthermocouple is applied to ya converter 550 which is energized from asource of alternating .current 551 to provide an output alternatingsignal. VIhe irst output terminal of converter 550 is connected througha resistor 552 to the first input terminal of an alternating currentamplifier 553. 'The second output terminal of converter 550 is connectedto ground. The second input terminal of ampli-tier 553 is connected tothe contactor of a potentiometer 554. The rst end terminal ofpotentiometer 554 is connected to a positive potential terminal 555, andthe second end terminal of potentiometer 554 is connected to ground. AfeedJback resistor 556 is connected between the output 19 terminal ofamplifier 553 and the first input terminal. The output terminal ofamplitier 553 is connected through capacitors. 557 and 558 to the firstterminal of a lprim-ary vwinding of a transformer 559, t-he `secondterminal of which isconnected to ground.

Amplifier 553 preferably is of the form illustrated in i FIGURE 3. Thisamplifier is represented by thetriodes 104, 106,111 and 118 of FIGURE 3.The first i'nput terminal'of amplier `553 is the control `grid of triode104, `and the second input terminal is the control grid of `triode 106.The cathode of triode 118 forms the output terminal of the linearampliiier. Resistors 552 and556 are selected so that the output signalof amplifier 553 is a linear function of the input signal.

The end terminal of the secondary. winding of transformer 559 isconnected to the control 'grid of respective triodes 560 and 561. Thecenter tap of the secondary winding of transformer 559 is connected toground. The anodes of triodes 560 and 561 are connected to a positivepotential terminal 562, and the cathodes of triodes 560 and 561 areconnected to ground throughl respective resistors 563 and564. Thetirstterminal of current source S51 is connected to the cathodes of triodes560 and 561 through respective capacitors 565 and 566. The cathode oftriode 560 is connected throughsresistors 567 and 56S `to the firstinput terminal of a direct `current amplifier 569. The cathode of triode561 is connected through resistors 561 and 572 to the second inputterminal of amplifier 569.- A capacitor 573 is Vconnected between groundand the junction between resisf tors 567-v and 568, and a capacitor 574is connected between ground and the junction between resistors 571 and572..r

Triodes 560 and 561 and the circuit elements connected thereto form aphase detector so that a direct voltage is applied to the inputoframplifler 569 which is proportional to the alternating output signallfrom ampliier-553. The second input terminal of amplifier 569 isconnected through a resistor 575 tothe contactor of a potentiometerk576. One end terminal of potentiometer 576 is con nected to a positivepotential terminal 577, land the` second end terminal of potentiometer576 is connected to ground. A feed-back resistor 580 is connectedbetween the output terminal of amplifier 569 ofthe rst input terminal.Amplifier 569 can-be of ythesame configuration asA ampliiier 553 exceptthat the output is linear.

The output terminal of amplifier 569 is connected to a terminal 581which is adapted to beengaged by a first switch 582.` A capacitor 583 isconnected between switch 582 and a switch 584 which engages a groundedterminal 585 'when switch 582 engage terminal 581. Switches 582 and 584are also adapted to engage respective termi,- nals 586 a-nd 587.Terminal 587 is connected to the rst input terminal of a direct currentamplifier 588, and terminal 586 is connected to the rstinput terminal ofamplifier 588 through a capacitor 589. Switches 582 and S84'are actuatedin unison by a solenoid 590 which is Venergized at a predeterminedfrequency by the output `sig- Y 594,l andthe second end terminal ofpotentiometer593 is connected to ground. A feed-back resistor 595iscon-V nectedy between the outputjterminal of 588 and termina] 586.- Aresistor 596 is connected between this terminal and ground.

The youtput signal from amplifier 569 is appliedto a storage andcomparison circuit which compareslevels Ystored on capacitor `583 is`applied to amplifier `588 1 through capacitor 589. Pulse generator 592'provides' signals `at `a low frequency so that the output signals 1from amplitier 569 are compared. successively-,with the@ originalsignal. If the reactor temperature` has a derivai tive, the output ofamplifier 588 represents tlfiisderiva-` tive superimposed on a D.C.level.

The output terminal of amplifier 588, which can be of the form ofamplifier 553, -is appliedthrough a capacitor 10 :598 to the rst inputterminal ofa chopper1599.; The.V

first input terminalof chopper 599 is connected to ground 4 througharesistor 600. The Vsecond input terminaly of chopper 599 is' connectedto` ground. Chopper 599 is i 4energized by current. source l551 toprovide an` output `signal of the frequency of source 551. This signalis applied to the input of an amplilier 601 which is tuned to: 1 passonly signals of the frequency of current source 551. The iirst outputterminal of amplifier 601 is connected through a resistor 213jto theinput of summing, ampli-l er 480 of FIGURE 8. The second outputyterminal of amplifier 601 is connected to ground.V

Capacitor 59S and `resistor 600 form a filter circuit which passes thederivative of the `reactor temperature which is at a frequencydetermined bythe pulse genera-` tor and which blocks the D.C.'.level.Thispassed 'signal is converted into a corresponding alternating signal,amplied and applied to the summing network of FIGURE i 8 so as tocompensate for any temperature. changes With-l in reactor 30. It,`should `be evident that the` circuit of FIGURE 10 isnot required if therateof change `of the temperature of reactor 10 is relatively small.

While the invention has been `described in conjunction with a presentpreferred embodiment, itobviously is not limited thereto.

What is claimed is: Y v 1. In a polymerizationprocess wherein thematerial to be polymerized and a catalyst are directed to apolymerization zone and the resulting products are removed from the.zone, a control system comprising means to measure the heat supplied tosaid zone, means to measure the heat removed from said zone, meanstomeasure the ditferencebetween thek heat supplied and theheat=re,` moved,means responsive to said `means to measurethe difference to control theoperation ofthe process= to tend to produce polymer at a uniform rate,means to measure the rate Aof temperature change of said` zone, andVmeans 4responsive to said means to measure the' rateofvtem-` peraturechange to adjust: said means to contro1.` n

2. The control system of claim 1 wherein saidmeans to measure `the rateof temperature change comprises means to establish `a irst signalrepresentative of the temperature of saidzone, means responsive to said`first signal to establish a second signal representative `ofthederivative ofl said iirst signalwith respect` to time,and` means totransmit an output signal representative :of said second signal atpreselected time intervals.

3. The control system of claim 1 wherein said means to measure the rateof temperature change comprises means to establish a rst signalrepresentative ofV the tempera'-4 ture of said zone, a signal storagemeans, differentiating means to establish an `output signalrepresentative ofthe derivative of an input Lsignal applied thereto,means to connect saidrst signal to said storage `means periodical-i ly,and means to connect said .storage means to the input of saiddifferentiating means periodically and at such times as said inputsignal is not being applied to said storage means.`

y 4. In a polymerization process wherein the material to bepolymerizedand a catalyst are directed toa polymerizationzone and theresulting products are removed from the Azone,.a control systemcomprising means to measure the rate lat which heat. is supplied to saidzone and toA establish a first -signal representative thereof, means t-omeasure the rateiat Mwhich heat isrremoved.from` said zone and toestablish a second signal representative thereof, means to measure therate of temperature change in said zone and to establish a third signalrepresentative thereof, means to sum algebraically said first, secondand third signal to establish a fourth signal representative of suchsum, and means responsive to said fourth signal to control the operationof the process to tend to produce polymer at a uniform rate, asindicated by said fourth signal remaining constant.

5. In a polymerization process wherein the material to be polymerizedand a catalyst are directed to a polymerization zone and the resultingproducts are removed from the zone, a system for establishing a signalwhich is representative of the rate at which polymer is producedcomprising means to measure the -rate at which heat is supplied to saidzone and to establish a first signal representative thereof, means tomeasure the rate at which heat is removed from said zone and toestablish a second signal representative thereof,'means to measure therate of temperature change in said zone and to establish a third signalrepresentative thereof, and means to sum algebraically said rst, secondand third signal to establish a fourth signal representative of suchsum, said fourth signal being representa-tive of the rate at whichpolymer is produced.

No references cited.

MALCOLM A. MORRISON, Primary Examiner.

K. W. DOBYNS, Assistant Examiner.

1. IN A POLYMERIZATION PROCESS WHEREIN THE MATERIAL TO BE POLYMERIZEDAND A CATALYST ARE DIRECTED TO A POLYMERIZATION ZONE AND THE RESULTINGPRODUCTS ARE REMOVED FROM THE ZONE, A CONTROL SYSTEM COMPRISING MEANS TOMEASURE THE HEAT SUPPLIED TO SAID ZONE, MEANS TO MEASURE THE HEATREMOVED FROM SAID ZONE, MEANS TO MEASURE THE DIFFERENCE BETWEEN THE HEATSUPPLIED AND THE HEAT REMOVED, MEANS RESPONSIVE TO SAID MEANS TO MEASURETHE